1- Yeah, still he was one of the most powerfull force user of his time. Since that in his time there was jedi masters and sith masters, he was as powerfull as them. How can you say that someone is a master of something? You'll say that you know about sidious and luke because George Lucas said that they are SW super-heroes. But what about other characters? Has obi-wan mastered light side? He was a jedi master, but that's only a title too...
The thing is, he was powerfull enough to be considered a master in both sides. Just play Kotor and you'll know that.

2- Yes, it's a character statement but they have no reason to lie about that, and since they are very good warriors and know a lot about war, it's a big deal. You can't say that he's not a skillful tactician or else he wouldn't be praised like this by a clan of WARRIORS.

3- Would have fallen? Could not control himself? What the hell are youtalking about? Have you made the dark side ending? That what would happen if he fallen to the dark side, he'd use the star forge to take the whole galaxy!!

1. How can someone be a master of something? Good question. The answer is not simple. Mastery requires the most serious mind. To show an unparelled control/use of an ability/skill. Being a Jedi Master does not make you a master of the Light Side. Obi-Wan is not a master of the Light Side. Mastering the Force is not something you can do. It requires you to be the picture of peace, tranquility. Mastering the Dark Side is even more difficult. The Dark Side becomes the master in almost every case.

2. They praised his use of tactics. Tactics that they themselves use. He used their own tactics to beat them. That's why they praised him. He used their tactics, not only that, but he bested them with it. No wonder they praised him!

3. What am I talking about? No need to get angry. Revan was absolutely corrupted by the Dark energies of Malachor V. He could not control these energies. They controlled him. Revan can't fathom what it takes to control the Dark Side. The Dark powers that he used would have corrupted him. That is what the Dark Side does. He doesn't have the mental discipline to control Dark powers.

Added Chapter 64 to The Shadows Fall"Your only hope to survive is to give in to the rage boiling within you, to acknowledge the Dark Side you deny, and tap into it!"--Darth Tyranus